Semiconductor package and manufacturing method thereof

ABSTRACT

The present disclosure provides a semiconductor structure. The semiconductor structure includes a carrier, a first redistribution layer (RDL) over the carrier, a semiconductor die over the first RDL, an adhesive layer between the semiconductor die and the first RDL, and a molding compound encapsulating the first RDL, the semiconductor die, and the adhesive layer. The first RDL includes at least one pattern electrically isolated from any component of the semiconductor structure. The present disclosure provides a method for manufacturing a semiconductor structure discussed herein. The method includes forming an RDL on a carrier, defining an active portion and a dummy portion of the RDL, and placing a semiconductor die over the dummy portion of the RDL.

FIELD

The present disclosure relates to a semiconductor package.

BACKGROUND

In the semiconductor industry, the fabrication of integrated circuits(IC) can be divided at least into three phases: wafer fabrication, ICfabrication process, and IC packaging. Each chip is fabricated throughwafer fabrication, circuit design, photolithography and etchingprocesses, and wafer dicing. After each chip formed based on the waferdicing is electrically connected to external signals through a bondingpad on the chip, the chip can be encapsulated by a sealant material. Thepackaging process protects the chip from heat, humidity, and noises andprovides an electrical connection medium between the chip and externalcircuits. By such means, packaging of the IC is completed.

Mobile devices such as mobile phones, mobile internet devices (MIDs) andlaptops, are designed with smaller form factor and slimmer profile forimproved aesthetic and functional appeals. The size of and real estateoccupied by semiconductor packages in the devices need to be scaled downaccordingly. Package-on-package (PoP) packaging technology is employedto stack a semiconductor package on top of another semiconductor packageto remove the x and y dimensions constraints in the layout ofsemiconductor packages on a motherboard. PoP allows verticallycombining, for example, discrete logic and memory ball grid array (BGA)packages. Two or more packages are installed on top of one another, e.g.stacked, with a standard interface to route signals between them. Thisallows higher density in the mobile device market.

Today's PoP semiconductor devices enjoy increasing popularity, becausethey promise to use components already developed and thus quicklyavailable, they are supposed to retain a slim space-saving contour afterassembly, and they are expected to be robust in terms of reliability inuse-test under variable temperature and moisture conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isemphasized that, in accordance with the standard practice in theindustry, various features are not drawn to scale. In fact, thedimensions of the various features may be arbitrarily increased orreduced for clarity of discussion.

FIG. 1 is a cross sectional view of a semiconductor structure accordingto some embodiments of the present disclosure;

FIG. 2 is a cross sectional view of a semiconductor package according tosome embodiments of the present disclosure;

FIG. 3 is a cross sectional view of a semiconductor package according tosome embodiments of the present disclosure;

FIG. 4 is a top view of a portion of a semiconductor package accordingto some embodiments of the present disclosure;

FIG. 5A to FIG. 5D are top views of a semiconductor package according tosome embodiments of the present disclosure;

FIG. 6A to FIG. 6D are top views of a semiconductor package according tosome embodiments of the present disclosure; and

FIG. 7A to FIG. 7K are a method for manufacturing a semiconductorstructure according to some embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

This description of illustrative embodiments is intended to be read inconnection with the accompanying drawings, which are to be consideredpart of the entire written description. In the description ofembodiments disclosed herein, any reference to direction or orientationis merely intended for convenience of description and is not intended inany way to limit the scope of the present invention. Relative terms suchas “lower,” “upper,” “horizontal,” “vertical,”, “above,” “below,” “up,”“down,” “top” and “bottom” as well as derivative thereof (e.g.,“horizontally,” “downwardly,” “upwardly,” etc.) should be construed torefer to the orientation as then described or as shown in the drawingunder discussion. These relative terms are for convenience ofdescription only and do not require that the apparatus be constructed oroperated in a particular orientation. Terms such as “attached,”“affixed,” “connected” and “interconnected,” refer to a relationshipwherein structures are secured or attached to one another eitherdirectly or indirectly through intervening structures, as well as bothmovable or rigid attachments or relationships, unless expresslydescribed otherwise. Moreover, the features and benefits of theinvention are illustrated by reference to the preferred embodiments.Accordingly, the invention expressly should not be limited to suchpreferred embodiments illustrating some possible non-limitingcombination of features that may exist alone or in other combinations offeatures; the scope of the invention being defined by the claimsappended hereto.

In the drawings, like reference numbers are used to designate like orsimilar elements throughout the various views and illustrativeembodiments of the present invention are shown and described. Thefigures are not necessarily drawn to scale, and in some instances thedrawings have been exaggerated and/or simplified in places forillustrative purposes only. One of ordinary skill in the art willappreciate the many possible applications and variations of the presentinvention based on the following illustrative embodiments of the presentinvention.

In a fan-out wafer level chip scale packaging (WLCSP) technique, 3-Delectrical interconnection with an interconnect I/O array throughvertical interconnects formed inside a footprint of semiconductor dieusually adopt a back-side RDL that extends the conduction path outsidethe footprint of the semiconductor die. For example, if a footprint of aDRAM package scales smaller than a footprint of a semiconductor diepackage positioned underneath, a back-side RDL close to thesemiconductor die package is introduced to provide a receiving point ofthe electrical signal and routing the signal through a fan-outconstruction, eventually guiding the signal to a front side of thesemiconductor die. In some embodiments of the present disclosure, theback-side RDL refers to an RDL formed close to a back side, instead of afront side, of a semiconductor die or a semiconductor die. The back sideof a semiconductor die or a semiconductor die is opposite to a frontside. The front side is where the contact pads, under bump metallization(UBM), and a front-side RDL are situated. However, the back-side RDL isnot limited to a PoP semiconductor package where vertical interconnectsare formed inside a footprint of semiconductor die. Verticalinterconnects formed outside a footprint of semiconductor die can alsoutilize the back-side RDL.

When a semiconductor die is placed on a back-side RDL using a fan-outpackaging technique, a die attached film (DAF) or an adhesive bondingfilm (ABF) is introduced between the semiconductor die and the back-sideRDL to physically adhere the semiconductor die and the back-side RDL. Aheating operation is followed after the semiconductor die placement, anda portion of the DAF or ABF is softened and flowing into a gap betweenadjacent patterns of the back-side RDL. However, the gap is notcompletely filled with the softened DAF or ABF, and several voids areformed in certain areas under the semiconductor die. Some voids occupyareas as large as areas with successful gap-fillings (i.e., no void).

The presence of voids creates weak spots on reliability test and causesthe semiconductor die loosely attached on the back-side RDL. Forexample, after the die placement and the heating operation immediatelyfollowed, a molding compound is applied to encapsulate the back-side RDLand the semiconductor die. Under certain circumstances, theloosely-attached die is easily shifted from its original positionbecause of a shear force exerted from the molding compound.Consequently, the subsequent patterns overlaid on the semiconductor dieturn out to be misaligned. Even under the condition when only a minorshift is occurred, the subsequent patterns are still landing onpositions that are out of specifications. The generation of voidsbetween the semiconductor die and the back-side RDL deteriorate theoverall reliability of the semiconductor package.

In some cases when the patterns of the back-side RDL are not even interms of the pattern heights, the semiconductor die is tilted after theplacement. For example, after the die placement and the heatingoperation immediately followed, a molding compound is applied toencapsulate the back-side RDL and the semiconductor die. A planarizationoperation (for example, a chemical mechanical polishing operation) issubsequently followed to expose a front side of the semiconductor die.Because the semiconductor die is tilted after the placement and hencethe total thickness variation of the semiconductor die is increased, theplanarization operation induces an over-grinding of the semiconductordie at a more elevated end of the tilted surface, damaging the contactpads, conductive plug, and under bump metallization (UBM) formed on thefront side of the semiconductor die.

Various means were implemented to solve the above-mentioned problemsbetween the semiconductor die and the back-side RDL. For example, whenheating up the sample after the semiconductor die placement, extendedheating duration (or increasing time for bonding) is applied to allow amore complete softening of the DAF or ABF, and hence a more integratedgap-filling. However, increasing the heating duration (or time forbonding) decreases the throughput of the semiconductor die pick andplacement. For instance, the manufacturing cost is increased more than 5times compared to a cost when a normal heating duration is used. Inanother example, a force exerted on the semiconductor die is increasedin order to enhance the adhesion between the semiconductor die and theback-side RDL. Observation shows the voids under the semiconductor diecannot be removed either by prolonging the heating duration or byapplying additional forces on the semiconductor die.

The present disclosure provides a back-side RDL structure which includesat least a dummy portion. In some embodiments, the dummy portion isdesigned to be as a same height as an active portion of the back-sideRDL. In certain embodiments, the dummy portion of the back-side RDL isprimarily used to resolve the incomplete gap-filling problem and thetilted semiconductor die as discussed above.

In some embodiments, a portion of the dummy portion of the RDL ispositioned outside a footprint of the semiconductor die. In otherembodiments, a footprint of the semiconductor die is greater than afootprint of the dummy portion of the RDL.

Compared to the package where only active portion is devised in theback-side RDL, an area ratio of the footprint of the dummy portion andthe semiconductor die is less is than 1.2.

In describing and claiming the present disclosure, the followingterminology will be used in accordance with the definitions set forthbelow.

As used herein, an “active portion” refers to a position on a patternwhich performs the actual computing and storage operations of thesemiconductor die. In some embodiments, an active portion of aredistribution layer (RDL) directs to some patterns of the RDL that areconnected to a through package via (TPV). In other embodiments, anactive portion of an RDL directs to some patterns of the RDL that areconnected to a TPV at a first side of the RDL and are connected to aconductive plug at a second side opposite to the first side of the RDL.

As used herein, a “dummy portion” refers to a position which does notform any electrical conductive path connected to the physical part of apackage that contains the transistors, resistors, and capacitors. Insome embodiments, the dummy portion is not limited to specific regionswithin a semiconductor package because whether the position forming anelectrical conductive path connected to the active structure depends onthe electrical routing design in individual packaging structure.

As used herein, “vapor deposition” refers to process of depositingmaterials on a substrate using a vapor phase of a material to bedeposited or a precursor of the material. Vapor deposition processesinclude any process such as, but not limited to, chemical vapordeposition (CVD) and physical vapor deposition (PVD). Examples of vapordeposition methods include hot filament CVD, rf-CVD, laser CVD (LCVD),conformal diamond coating processes, metal-organic CVD (MOCVD),sputtering, thermal evaporation PVD, ionized metal PVD (IMPVD), electronbeam PVD (EBPVD), reactive PVD, atomic layer deposition (ALD), plasmaenhanced CVD (PECVD), high density plasma CVD (HDPCVD), low pressure CVD(LPCVD), and the like.

As used herein, “molding compound” refers to a compound formed withcomposite materials. A molding compound may include epoxy resins,phenolic hardeners, silicas, catalysts, pigments, mold release agents,or the like. Material for forming a molding compound has a high thermalconductivity, a low moisture absorption rate, a high flexural strengthat board-mounting temperatures, or a combination thereof.

As used herein, “electrical interconnects” refers to conductive lines orfilms routed inside the IC structure over and around the die or dies. Insome embodiments, the electrical interconnects are redistribution layers(RDL). The RDLs are used for a fan-in or a fan-out process. In someembodiments, the electrical interconnects are formed with a conductivematerial such as gold, silver, copper, nickel, tungsten, aluminum,and/or alloys thereof.

As used herein, a “through package via (TPV)” refers to a conductivefilled via or a conductive plug that is disposed on a carrier, asubstrate, or embedded in a molding compound. The conductive filled viaor a conductive plug is arranged to extend to a top surface of thepackage or the molding compound. Conductive posts may provide anelectrical communication between a top surface and a bottom surface ofthe package or provide an electrical communication between a top surfaceof the package to a chip in the package.

As used herein, a “contact pad” is disposed on a top surface of a die. Atop surface of the contact pad may receive a solder ball or solder pasteand acts as a terminal to connect the die to an external circuit orelectrically connects to an RDL. A bottom surface of the contact pad iseither connected to an interconnect, such as an RDL, or to an activearea in the die. In some embodiments, the contact pad is an under bumpmetallization (UBM). In some embodiments, the UBM is formed with aconductive material such as gold, silver, copper, nickel, tungsten,aluminum, and/or alloys thereof.

As used herein, a “patterning” or “patterned” is used in the presentdisclosure to describe an operation of forming a predetermined patternon a surface. The patterning operation includes various steps andprocesses and varies in accordance with features of embodiments. In someembodiments, a patterning operation patterns an existing film or layer.The patterning operation includes forming a mask on the existing film orlayer and removing the unmasked portion of the film or layer with anetch or other removal process. The mask is a photo resist or a hardmask.In some embodiments, a patterning operation directly forms a patternedlayer on a surface. The patterning operation includes forming aphotosensitive film on the surface, conducting a photolithographyprocess and a developing process. The remaining photosensitive film maybe removed or retained and integrated into the package.

As used herein, “plating” or “plated” is used in the present disclosureto describe an operation of forming a film or a layer on a surface. Theplating operation includes various steps and processes and varies inaccordance with features of embodiments. The film or layer plated on thesurface may be a single film or a composite stack. In some embodiments,a plating operation forms a metallic film. In some embodiments, aplating operation includes forming a seed layer and electroplating ametallic film on the seed layer.

As used herein, “filling” or “filled” is used in the present disclosureto describe an operation of forming material in a hole. The fillingoperation includes various steps and processes and varies in accordancewith features of embodiments. In some embodiments, a filling operationincludes forming a conductive material in a hole. In some embodiments, afilling operation includes forming a liner on the sidewalls of the holeand forming a conductive film on the liner. In some embodiments, afilling operation includes an electroplating process. In someembodiments, a filling operation includes a vapor deposition process. Insome embodiments, a filling operation includes a sputtering process.

Referring to FIG. 1, a semiconductor structure 300 including twopackages are shown in a cross sectional view. The cross section of thesemiconductor structure 300 is an X-Z plane according to the Cartesiancoordinate system labeled in FIG. 1. A positive Y direction is pointinginto the paper, and a negative Y direction is pointing toward thereader. A semiconductor package 100 is electrically connected to asemiconductor package 200 through several conductive plugs 112. In someembodiments, the semiconductor structure 300 is a package-on-package(PoP) structure. In certain embodiments, the semiconductor packages 100and 200 include a microprocessor package, a memory package (including adynamic random access memory or a flash memory), application specificintegrated circuits (ASIC), logic circuits, analog circuits, radiofrequency (RF) circuits, discrete devices, or other semiconductor die orelectrical components. In certain embodiments, the semiconductorstructure 300 is part of a cellular phone, personal digital assistant(PDA), digital video camera (DVC), or other electronic communicationdevice. Alternatively, the semiconductor structure 300 is a graphicscard, network interface card, or other signal processing card that canbe inserted into a computer.

Referring to semiconductor package 100 in FIG. 1, the semiconductorpackage 100 includes a carrier 101 having a front surface and a backsurface opposite to the front surface. The front surface of the carrier101 refers to the surface in proximity to a semiconductor die 105. Insome embodiments, the carrier 101 has several layers including, but notlimited to, a solder resist layer, a laminating compound layer, and anadhesive bonding film. A patterned seed layer 113 is attached to thefront surface of the carrier 101. In some embodiments, the seed layer113 includes multiple layers of selectively plated Ni/Au, Ti/Cu, orTi/Cu/NiV/Cu. A first redistribution layer (103A, 103B, 103C) is incontact with a portion of the seed layer 113. A semiconductor die 105 isfurther attached to the first redistribution layer (103A, 103B, 103C)through an adhesive layer 107. In some embodiments, the adhesive layer107 is a die attach film (DAF). In certain embodiments, a footprint ofthe semiconductor die 105 at least covers a pattern 103A of the firstredistribution layer 103. In other embodiments, a footprint of thesemiconductor die 105 is smaller than the pattern 103A of the firstredistribution layer 103. More detailed discussion to the footprint ofthe semiconductor die 105 and the footprint of the pattern 103A of thefirst redistribution layer 103 can be referred to FIGS. 5A to 6D in thepresent disclosure.

In FIG. 1, two patterns 103B and 103C in the first redistribution layer103 are electrically connected to a through package via (TPV) 111,respectively. One end of the TPV 111 is electrically coupled to thefirst redistribution layer (103B, 103C), and the other end of the TPV111 is electrically coupled to a front side of the semiconductor die105B through a second redistribution layer 103′. In certain embodiments,the semiconductor die 105 includes a front side 105B and a back side105A. The back side 105A of the semiconductor die 105 is attached to thefirst redistribution layer 103 through an adhesive layer 107, and thefront side 105B of the semiconductor die 105 includes electricalconnections to devices or semiconductor structures outside of thesemiconductor package 100. The electrical connection on the front side105B includes, but no limited to, contact pads, under bumpmetallization, and metal bumps.

In FIG. 1, at least one pattern 103A in the first redistribution layeris electrically isolated from any component of the semiconductor package100. Compared to the two patterns 103B and 103C in the firstredistribution layer 103, the at least one pattern 103A is surroundedand covered by the adhesive layer 107. In some embodiments, the twopatterns 103B and 103C is an active portion of the first redistributionlayer 103, and the pattern 103A is a dummy portion of the firstredistribution layer 103. In certain embodiments, the dummy portion 103Aof the first redistribution layer 103 is not connected to any conductivepath in all directions.

Referring to semiconductor packages 100 and 200 in FIG. 1, a moldingcompound 109 in package 100 encapsulates the first redistribution layer103, the semiconductor die 105, and the adhesive layer 107. A moldingcompound 209 in package 200 encapsulates the semiconductor devices 205and the electrical connections bridging the electronic signal betweenthe semiconductor devices 205 in the package 200 and the semiconductordevices 105 in the package 100. In some embodiments, the conductiveplugs 112 penetrate through the carrier 101 of the semiconductor package100, connecting the first redistribution layer 103 at one end, andconnecting contact pads of the semiconductor package 200 at the otherend.

As shown in FIG. 1, the semiconductor structure 300 using a PoPtechnique has an electronic device 205 in package 200 and asemiconductor die 105 in package 100. In some embodiments, a footprint,or a projection area, of the electronic device 205 is greater than afootprint, or a projection area, of the semiconductor die 105. Aconductive path between the semiconductor device 205 and firstredistribution layer 103 extends from an active surface 205A of theelectronic device 205 to a contact pad 201A positioned on a carrier 201through bonding wires 211. The conductive path further penetrates thecarrier 201 through a through carrier via 212, connecting to theconductive plug 112, and landing on a conductive stack composing of theseed layer 113 and the active portion (103B, 103C) of the firstredistribution layer 103 in the semiconductor package 100. In someembodiments, the conductive plug 112 in the conductive path does nothave to land on the conductive stack composing of the seed layer 113 andthe active portion (103B, 103C) of the first redistribution layer 103.Instead, the conductive plug 112 lands on a seed layer 113 immediatelyconnecting to a TPV 111. In other embodiments, the TPV 111 in package100 is electrically connected to electronic components other than device205 in the package 200.

FIG. 2 is a cross sectional view of a semiconductor structure accordingto some embodiments of the present disclosure. In some embodiments, thesemiconductor structure is a semiconductor package 100A. Referring toFIG. 1 and FIG. 2, the semiconductor package 100A and the semiconductorpackage 100 are interchangeable. Elements with same labeling numbers asthose in the semiconductor package 100 in FIG. 1 are previouslydiscussed with reference thereto and are not repeated here forsimplicity.

In FIG. 2, a semiconductor package 100A shows two semiconductor dies 105prior to a wafer die sawing. Individual semiconductor dies are obtainedwhen a die sawing machine separates the two dies through a line AA′. Adummy portion 103A of the first redistribution layer 103 is supporting aback side 105A of the semiconductor die 105. The dummy portion 103A ofthe first redistribution layer 103 is electrically isolated from othercomponents in the package 100A because a top surface 1033 and a sidewall1031 of the dummy portion 103A are in contact with an adhesive layer107. In some embodiments, the adhesive layer is composed of insulatingmaterials. A carrier 101 in the semiconductor package 100A includes asubstrate 101A, a releasable layer 101B, and a gluing layer 101C. Insome embodiments, the substrate 101A contains dummy or sacrificial basematerial such as silicon (Si), polymer, polymer composite, metal,ceramic, glass, glass epoxy, beryllium oxide, or other suitablelow-cost, rigid material or bulk semiconductor material for structuralsupport. In some embodiments, the releasable layer 101B containsmaterial which decomposes by energy (including heat or light)irradiation. In some embodiments, the gluing layer contains apolymer-based layer such as a polybenzobisoxazole (PBO) film or anadhesive bonding film.

FIG. 3 is a cross sectional view of a semiconductor structure accordingto some embodiments of the present disclosure. In some embodiments, thesemiconductor structure is a semiconductor package 100B. Referring toFIG. 1 and FIG. 3, the semiconductor package 100B and the semiconductorpackage 100 are interchangeable. Referring to FIG. 1 and FIG. 3, thesemiconductor package 100B and the semiconductor package 100 areinterchangeable. Elements with same labeling numbers as those in thesemiconductor package 100 in FIG. 1 are previously discussed withreference thereto and are not repeated here for simplicity.

In FIG. 3, a second redistribution layer 103′ is positioned on a frontside 105B of the semiconductor die 105. The active portion 103B and 103Cof the first redistribution layer 103 is electrically connected to thesecond redistribution layer 103′ through a through package via (TPV)111. The TPV not landing on the first redistribution layer 103 connectsto a seed layer 113 at one end and connects to the second redistributionlayer 103′ at the other end. As shown in FIG. 3, a first redistributionlayer 103 is in proximity to a back side 105A of the semiconductor die105. A second redistribution layer 103′ is in proximity to a front side105B of the semiconductor die 105.

In certain embodiments, a ball grid array containing several solderballs 115 is placed over the first redistribution layer 103′. The solderball 115 includes eutectic Sn/Pb, high-lead solder, or lead-free solder.In certain embodiments, under bump metallization (UBM) (not shown) ispositioned in the second redistribution layer 103′, receiving the solderballs 115. UBM contains multiple layers of selectively plated Ni/Au,titanium (Ti)/Cu, titanium tungsten (TiW)/Cu, Ti/Cu/nickel vanadium(NiV)/Cu, or the combination thereof. In addition to the solder ball,other interconnect structure is used in other embodiments. For example,stud bump or micro bump. In certain embodiments, UBM provide bondablepads for bonding with various bumps, and further provide a barrier tometal diffusion.

FIG. 4 is a top view of a semiconductor structure according to someembodiments of the present disclosure. Referring to the Cartesiancoordinate in FIGS. 2-3 and FIG. 4, the top view in FIG. 4 shows an X-Yplane of the semiconductor structures 100A and 100B in FIG. 2 and FIG.3, respectively. In some embodiments, FIG. 4 is a top view of a rightportion (framed in dotted lines) of the semiconductor package 100B inFIG. 3. In other is words, the right portion of the semiconductorpackage 100B in FIG. 3 is a cross section sectioning along line BB′ inFIG. 4. For clarity purpose, the semiconductor die 105 and the secondredistribution layer 103′ are not shown in FIG. 4. In some embodiments,the dummy portion 103A of the first redistribution layer 103 ispositioned in the middle of the semiconductor package 100B. In certainembodiments, the active portion 103B and 103C of the firstredistribution layer 103 surrounds the dummy portion 103A. Several TPVs111 are arranged on the active portion 103B and 103C. In addition, moreTPVs 111 are situated at positions without the first redistributionlayer 103.

Referring to FIG. 4, in some embodiments, the TPVs 111 on the activeportion 103B and 103C of the first redistribution layer 103 extend theconductive trace back to a semiconductor die (not shown) positioned overthe dummy portion 103A. In other embodiments, the TPVs 111 on the activeportion 103B and 103C of the first redistribution layer 103 extend toother directions connecting to devices other than the semiconductor die105 (not shown in FIG. 4). In certain embodiments, TPVs 111 situated onpositions without the first redistribution layer 103 are in directcontact with the seed layer 113 shown in FIG. 3. In some embodiments,TPVs 111 landing on the seed layer 113 extend outwards to connect withexternal contacts 117. However, in certain embodiments, the TPVs 111landing on the seed layer 113 connects back to the contact pads on afront surface 105B of the semiconductor die 105 (not shown in FIG. 4).

Referring to FIG. 3, FIG. 4, and FIG. 5A to FIG. 5D, wherein FIG. 5A toFIG. 5D are top views of a semiconductor package according to someembodiments of the present disclosure. Compared to FIG. 4, FIG. 5A toFIG. 5D show only a footprint area A1 of the dummy portion 103A in thefirst redistribution layer 103 and a footprint area A2 of thesemiconductor die 105 positioned on the first redistribution layer 103,whereas FIG. 4 shows a top profile of the TPV 111 and conductive traces.In some embodiments, the footprint area A1 is a projection area of thedummy portion 103A, and the footprint area A2 is a projection area ofthe semiconductor die 105. When observing a top view from a front sideof a semiconductor die 105, the footprint area A1 of the dummy portion103A is under the footprint area A2 of the semiconductor die 105 andthus the view of the dummy portion 103A shall be blocked. For claritypurpose, the footprint area A1 of the dummy portion 103A is shown inFIGS. 5A to 5D in order to compare sizes of the area A1 and area A2.

In some embodiments, the dummy area 103A is visible by an X-rayscanning. In other embodiments, the dummy area 103 is shown by removingthe semiconductor die 105 and the adhesive layer 107 covering above andaround the dummy area 103.

In FIG. 5A to FIG. 5D, the footprint area A2 of the semiconductor die105 is greater than the footprint area A1 of the dummy portion 103A. Insome embodiments, the footprint area ratio A1/A2 is within a range offrom about 0.3 to about 0.8. For example, in FIG. 5A to FIG. 5D, thefootprint area ratio A1/A2 is about 0.75, 0.3, 0.45, and 0.5,respectively. In some embodiments, the dummy portion 103A includesseveral patterns. For example, the dummy portion shown in FIG. 5Bcontains four squares. In other embodiments, the dummy portion 103Aincludes polygonal shapes such as tetragonal shape or triangle. Incertain embodiments, the dummy portion 103A includes irregular shapesmixing curved and straight boundaries.

Referring to FIG. 5A to 5D, in some embodiments, the dummy portion 103Ais symmetric to a geometric center G. For example, in FIG. 5C, the dummyportion 103 A is a cross shape with a geometric center G. The crossshape at least has a four fold symmetry with respect to the geometriccenter G. In FIG. 5B, even the dummy portion 103A is not a singlecontinuous area, a geometric center G is identified taking the foursquares into account. Similarly, the four square arrangement has atleast a four fold symmetry with respect to the geometric center G.

Referring to FIG. 3, FIG. 4, and FIG. 6A to FIG. 6D, wherein FIG. 6A toFIG. 6D are top views of a semiconductor package according to someembodiments of the present disclosure. Compared to FIG. 4, FIG. 6A toFIG. 6D show only a footprint area A1 of the dummy portion 103A in thefirst redistribution layer 103 and a footprint area A2 of thesemiconductor die 105 positioned on the first redistribution layer 103,whereas FIG. 4 shows a top profile of the TPV and the conductive traces.In some embodiments, the footprint area A1 is a projection area of thedummy portion 103A, and the footprint area A2 is a projection area ofthe semiconductor die 105. When observing a top view from a front sideof a semiconductor die 105, the footprint area A1 of the dummy portion103A is under the footprint area A2 of the semiconductor die 105 andthus the view of the dummy portion 103A shall be blocked. For claritypurpose, the footprint area A1 of the dummy portion 103A is shown inFIGS. 6A to 6D in order to compare sizes of the footprint area A1 andthe footprint area A2.

In FIG. 6A to FIG. 6D, a portion of the patterns of the dummy portion103A is situated outside the footprint area A2 of the semiconductor die105. In some embodiments as shown in FIG. 6A, a part of the dummyportion 103A is situated outside the footprint area A2 of thesemiconductor die 105, and the footprint area ratio A1/A2 is greaterthan unity. Thus, only a footprint area A1 of the dummy portion 103A isshown in FIG. 6A because the footprint area A2 of the semiconductor die105 is completely covered by the footprint area A1, and only a dottedline is delineated showing the boundary of the footprint area A2. Inother embodiments as shown in FIG. 6B, a part of the dummy portion 103Ais situated outside the footprint area A2 of the semiconductor die 105,but the footprint area ratio A1/A2 is below unity. In some embodiments,the footprint area ratio A1/A2 is within a range of from about 0.5 toabout 1.2. For example, in FIG. 6A to FIG. 6D, the footprint area ratioA1/A2 is about 1.2, 0.0.5, 0.8, and 0.6, respectively.

Referring to FIG. 6A to 6D, in some embodiments, the dummy portion 103Aincludes several patterns. For example, the dummy portion shown in FIG.6B contains five squares. In other embodiments, the dummy portion 103Aincludes polygonal shapes such as tetragonal shape or triangle. Incertain embodiments, the dummy portion 103A includes irregular shapesmixing curved and straight boundaries. In some embodiments, the dummyportion 103A is symmetric to a geometric center G. For example, in FIG.6C, the dummy portion 103 A is a cross shape with a geometric center G.The cross shape at least has a two fold symmetry with respect to thegeometric center G. In FIG. 6D, even the dummy portion 103A contains twoopposite triangles, a geometric center G is identified taking the twoopposite triangles into account. Similarly, the two-triangle arrangementhas at least a two-fold symmetry with respect to the geometric center G.

FIG. 7A to FIG. 7K are various operation in a method for manufacturing asemiconductor structure in the present disclosure. In FIG. 7A, a firstredistribution layer 103 is patterned on a carrier 101. In someembodiments, the patterning operation is conducted by photolithography.Photolithography includes forming a pattern in reticles or a photomask(not shown) and transferring the pattern into a surface layer of thecarrier 101. In other embodiments, the patterning operation includespatterning materials by directly depositing the material into the areasor voids formed by a previous deposition/etch operation using techniquessuch as electroless and electrolytic plating. In certain embodiments,the first redistribution layer 103 is formed over a surface of thecarrier 101 using evaporation, electrolytic plating, electrolessplating, screen printing, or other suitable metal deposition process.The first redistribution layer 103 provides for electrical communicationbetween each of the semiconductor packages, mounted components, andother external system components. The first redistribution layer 103also provides power and ground connections to each of the semiconductorpackages.

As shown in FIG. 7A, the carrier 101 contains a substrate 101A and amultilayer (101B, 101C, 101D) stack positioned on the substrate 101A. Insome embodiments, the multilayer stack includes a releasable layer 101B,a gluing layer 101C, and a seed layer 113. The releasable layer 101Bcontains material which decomposes by energy (including heat or light)irradiation. The gluing layer contains a polymer-based layer such as apolybenzobisoxazole (PBO) film or an adhesive bonding film. In certainembodiments, the gluing layer is formed by a spin coating operation. Incertain embodiments, the seed layer 113 contains multiple layers ofselectively plated Ni/Au, titanium (Ti)/Cu, titanium tungsten (TiW)/Cu,Ti/Cu/nickel vanadium (NiV)/Cu, or their combination, and is formed byPVD, CVD, sputtering, electrolytic plating, electroless plating, metalevaporation, metal sputtering, or other suitable metal depositionprocess. In certain embodiments, the seed layer 113 has a thickness offrom about 50 nm to about 100 nm.

Referring to FIG. 7B, several through package vias (TPVs) are formedover the first redistribution layer 103. In some embodiments, theformation of the TPVs includes filling conductive materials in the voidspreviously formed in a hard mask or a photoresist layer 111′ throughPVD, CVD, sputtering, electrolytic plating, electroless plating, metalevaporation, or a metal sputtering operation. Forming the TPVs atpredetermined region defines an active portion (103B, 103C) and a dummyportion 103A in the first redistribution layer 103. For example, Theactive portion (103B, 103C) includes at least one TPV landing on a topsurface of that specific pattern of the first redistribution layer 103,and the TPV connects the electrical signal from the active portion(103B, 103C) to other signal-receiving components in the semiconductorpackage. On the other hand, the dummy portion 103A is not contacting toany TPVs, but is electrically coupled to other patterns in the firstredistribution layer 103 through the underlying seed layer 113. As shownin FIG. 7B, some TPVs are formed on a surface of the carrier 101 insteadof on the active portion (103B, 103C) of the first redistribution layer103.

FIG. 7C shows a removal of the hard mask or the photoresist layer 111′after the formation of the TPVs, and followed by an etch separating theseed layer 113 under each pattern (103A, 103B, 103C) of the firstredistribution layer 103. The dummy portion 103A is neither contactingto any TPVs nor connecting to other patterns (103B, 103C) in the firstredistribution layer 103. In other words, the dummy potion 103A iselectrically isolated from other components in the semiconductorpackage.

Referring to FIG. 7D, two semiconductor dies 105 are placed on the firstredistribution layer 103. In some embodiments, placing the semiconductordie 105 includes applying a die attached film (DAF) 107 on a back side105A of the semiconductor die 105, and followed by an annealingoperation to soften the DAF 107, allowing the DAF 107 to fill a gapbetween adjacent patterns of the first redistribution layer 103. In someembodiments, the annealing operation is omitted. Note that thesemiconductor die 105 is placed at least over the dummy portion 103A. Insome embodiments, a footprint of the semiconductor die 105 covers thedummy portion 103A and a part of the active portion (103B, 103C). Inother embodiments, a footprint of the semiconductor die 105 covers onlya part of the dummy portion 103A. The footprint area ratio between thesemiconductor dies 105 and the dummy portion 103A are previouslydiscussed with reference to FIG. 5A to FIG. 6D of the present disclosureand are not repeated here for simplicity. Because the back side 105A ofthe semiconductor die 105 is facing the dummy portion 103A of the firstredistribution layer 103, in some embodiments, the first redistributionlayer 103 is called a back-side redistribution layer.

In FIG. 7E, a molding compound 109 is applied to the semiconductorpackage to encapsulate the first redistribution layer 103, thesemiconductor dies 105, and the adhesive is layer 107. In someembodiments, a planarization operation is conducted after theencapsulation to remove excess material over the semiconductor die 105and a top surface 111 a of the TPVs from a front side 105B. Theplanarization operation involves polishing the surface of thesemiconductor package with a polishing pad. An abrasive material andcorrosive chemical are added to the surface of the wafer duringpolishing. The combined mechanical action of the abrasive and corrosiveaction of the chemical removes any irregular topography, resulting in auniformly flat surface.

FIG. 7F shows a second redistribution layer 103′ is formed on the frontside 105B of the semiconductor die 105. In some embodiments, apatterning operation is utilized to form the conductive traces in thesecond redistribution layer 103′. As shown in FIG. 7F, a conductive pathstarting from the seed layer 113 and the active portion (103B, 103C) ofthe first redistribution layer 103 is connected to the secondredistribution layer 103′ through a TPV 111. Another conductive path isformed starting from the seed layer 113 to the first redistributionlayer 103′ through another TPV 111. Note none of the conductive path isformed from the dummy portion 103A of the first redistribution layer 103to the second redistribution layer 103′.

FIG. 7G to FIG. 7K is a series of operation to complete individualsemiconductor packages. In FIG. 7G, a ball grid array (BGA) is formed onthe second redistribution layer 103′. In some embodiments, the BGA isformed by a ball dropping, a screen printing, or a stencil printingoperation. In FIG. 7H, the substrate layer 101A of the carrier 101 isde-bonded by light irradiation or heat. In some embodiments, thereleasable layer 101B is configured to degrade and generating defectsand voids under the irradiation of UV light or laser. When thedegradation reaches a certain point, a portion of the semiconductorpackage over the gluing layer 101C are detached from the substrate layer101A. The detached semiconductor package is then inverted and a sidehaving the BGA 115 is placed on a blue tape 117. In some embodiments,several layers of tapes are laminated on the gluing layer 101C forprotection and warpage balance. The protecting tape includes solderresist, laminating compound, or adhesive bonding film. In otherembodiments, lamination of the protecting tape is omitted.

FIG. 7I shows a drilling operation opening holes 111 b at predeterminedpositions for electrical conduction. In some embodiments, the drillingoperation includes a laser drill, followed by a post-drill cleaning toremove the residue during the operation. In some embodiments, the holes111 b are opened in the gluing layer 101C, on the active portion (103B,103C) of the first redistribution layer 103. In other embodiments, theholes 111 b are opened in the gluing layer 101C, over a TPV 111 withoutcontacting to a first redistribution layer 103. FIG. 7J shows a resultof semiconductor die 105 singulation. In some embodiments, thesemiconductor package shown in FIG. 7I is scored and broken alongnon-functional regions of the package called saw streets or scribes. Thepackage is singulated using a laser cutting tool or saw blade. In someembodiments, only one semiconductor die 105 is encapsulated in asingulated package. In other embodiments, more than one semiconductordie 105 is encapsulated in a singulated package. As shown in FIG. 7J, insome embodiments, an organic surface protection (OSP) is applied to abottom 111 c of the hole 111 b. OSP is an organic solution based on animidazole substitute which, by means of dipping or rinsing can beselectively applied to a metal surface, ready for soldering. A thintransparent OSP layer covers a surface of the exposed seed layer 113like a barely visible clear varnish.

Referring to FIG. 7K, the singulated package shown in FIG. 7J iselectrically connected to another semiconductor package 200′ throughseveral conductive plugs 112. Note the semiconductor package 200′differs from the semiconductor package 200 shown in FIG. 1 in that thesemiconductor device 205′ encapsulated in the package 200′ has a smallerfootprint than the footprint of the semiconductor die 105 in thesemiconductor package 100. Under such condition, a conductive pathbetween the semiconductor device 205′ and first redistribution layer 103extends from an active surface 205′A of the electronic device 205′ to acontact pad 201′A positioned on a carrier 201′ through bonding wires211′. The conductive path further penetrates the carrier 201′ through athrough carrier via 212′, connecting to the conductive plug 112, andlanding on a conductive stack composing of the seed layer 113 and theactive portion (103B, 103C) of the first redistribution layer 103 in thesemiconductor package 100. The conductive stack extends out from thefootprint of the semiconductor die 105 and electrically connected to asecond redistribution layer 103′ by TPVs 111. In some embodiments, anadditional underfill 123 is introduced between the semiconductorpackages 200′ and 100, in order to provide additional mechanical supportto the conductive plug 112 in a mobile device.

In some embodiments, a semiconductor structure in a present disclosureincludes a carrier, a first redistribution layer (RDL) over the carrier,a semiconductor chip over the RDL, an adhesive layer between thesemiconductor chip and the RDL, and a molding compound encapsulating thefirst RDL, the semiconductor chip, and the adhesive layer. The first RDLincludes at least one pattern electrically isolated from any componentof the semiconductor structure.

In certain embodiments, the first RDL is electrically connected to asemiconductor package. In certain embodiments, a back side of thesemiconductor chip is in proximity to the first RDL. In certainembodiments, the semiconductor structure further includes a second RDLpositioned on a front side of the semiconductor chip.

In some embodiments, a package-on-package (PoP) semiconductor structureprovided in the present disclosure includes a carrier, a redistributionlayer (RDL) comprising an active portion and a dummy portion attachingto the carrier, and a semiconductor chip attaching to the RDL by anadhesive layer. A portion of the semiconductor chip attaches to thedummy portion of the RDL and the RDL is electrically coupled to asemiconductor package via a conductive plug passing through the carrier.

In certain embodiments, a portion of the dummy portion of the RDL ispositioned outside a projection area of the semiconductor chip. In otherembodiments, a projection area of the semiconductor chip is greater thana projection area of the dummy portion of the RDL.

In certain embodiments, an area ratio of the projection area of thedummy portion of the RDL and the projection area of the semiconductorchip is less than 1.2. In certain embodiments, the RDL is in contact toa back side of the semiconductor chip.

In some embodiments, a method of manufacturing a semiconductor structureas discussed in the present disclosure is provided. The method includesforming a redistribution layer (RDL) on a carrier, defining an activeportion and a dummy portion of the RDL, and placing a semiconductor chipat least over the dummy portion of the RDL.

In certain embodiments, the operation of defining an active portion anda dummy portion of the RDL includes plating a through package via (TPV)on the active portion of the RDL.

In certain embodiments, the operation of placing a semiconductor chip atleast over the dummy portion of the RDL includes facing a back side ofthe semiconductor chip to the dummy portion of the RDL.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations cancan be made herein without departing from the spirit andscope of the invention as defined by the appended claims. For example,many of the processes discussed above cancan be implemented in differentmethodologies and replaced by other processes, or a combination thereof.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure of the present invention, processes,machines, manufacture, compositions of matter, means, methods, or steps,presently existing or later to be developed, that perform substantiallythe same function or achieve substantially the same result as thecorresponding embodiments described herein may be utilized according tothe present invention. Accordingly, the appended claims are intended toinclude within their scope such processes, machines, manufacture,compositions of matter, means, methods, or steps.

What is claimed is:
 1. A semiconductor structure, comprising: a carrier;a first redistribution layer (RDL) over the carrier, comprising at leastone pattern electrically isolated from any component of thesemiconductor structure; a semiconductor die over the first RDL; anadhesive layer between the semiconductor die and the first RDL; and amolding compound, encapsulating the first RDL, the semiconductor die,and the adhesive layer.
 2. The semiconductor structure in claim 1,further comprising a through package via (TPV) penetrating the moldingcompound.
 3. The semiconductor structure in claim 2, wherein the TPV iselectrically connected to a semiconductor package
 4. The semiconductorstructure in claim 1, wherein the first RDL is electrically connected toa semiconductor package.
 5. The semiconductor structure in claim 4,wherein the semiconductor package comprises a DRAM package, a processorpackage, or a flash memory package.
 6. The semiconductor structure inclaim 1, a back side of the semiconductor die is in proximity to thefirst RDL.
 7. The semiconductor structure in claim 1, further comprisinga second RDL on a front side of the semiconductor die.
 8. Thesemiconductor structure in claim 1, a sidewall and a top surface of theat least one pattern of the first RDL is surrounded by the adhesivelayer.
 9. A package-on-package (PoP) semiconductor structure,comprising: a carrier; a redistribution layer (RDL) comprising an activeportion and a dummy portion attaching to the carrier; and asemiconductor die attaching to the RDL by an adhesive layer, wherein aportion of the semiconductor die is attaching to the dummy portion ofthe RDL, and wherein the RDL is electrically coupled to a semiconductorpackage via a conductive plug passing through the carrier.
 10. The PoPsemiconductor structure in claim 9, wherein a portion of the dummyportion of the RDL is positioned outside a projection area of thesemiconductor die.
 11. The PoP semiconductor structure in claim 9, anarea ratio of a projection area of the dummy portion of the RDL and aprojection area of the semiconductor die is less than 1.2.
 12. The PoPsemiconductor structure in claim 9, a projection area of thesemiconductor die is greater than a projection area of the dummy portionof the RDL.
 13. The PoP semiconductor structure in claim 9, wherein thedummy portion of the RDL comprises a plurality of patterns.
 14. The PoPsemiconductor structure in claim 9, an arrangement of the dummy portionof the RDL is symmetric to a geometric center of the semiconductor die.15. The PoP semiconductor structure in claim 9, wherein the dummyportion of the RDL comprises a polygonal shape.
 16. The PoPsemiconductor structure in claim 9, wherein the RDL is in contact to aback side of the semiconductor die.
 17. The PoP semiconductor structurein claim 9, wherein a dummy portion of the RDL is surrounded by theadhesive layer.
 18. A method of manufacturing a semiconductor structure,comprising: forming a redistribution layer (RDL) on a carrier; definingan active portion and a dummy portion of the RDL; and placing asemiconductor die over the dummy portion of the RDL.
 19. The method inclaim 18, wherein the defining an active portion and a dummy portion ofthe RDL comprises plating a through package via on the active portion ofthe RDL.
 20. The method in claim 18, wherein the placing a semiconductordie at least over the dummy portion of the RDL comprises facing a backside of the semiconductor die to the dummy portion of the RDL.